How the comet has changed since the summer: the red dot showing the brightest pixel appears to have reversed direction (Picture: David Jewitt,Jane Luu,astro-ph.EP)
Mysterious comet 3l/ATLAS has just done something which looks like ‘controlled manouevering’,according to the scientist who made headlines claiming it could be an alien spacecraft.
The interstellar space rock was spotted in July,and is expected to pass back out of our solar system and into outer space… Unless there’s someone at the controls who might have other ideas?
Before you start panic buying toilet paper,we should point out that his theories are not widely accepted by other space researchers.
In fact,they’ve been made ‘to the annoyance of a lot of people who actually work on comets’,astrophysicist Dr Mark Norris told Metro.
But they are nevertheless making headlines,because Dr Avi Loeb,a controversial Harvard astrophysicist,has claimed the latest images could show it deployed ‘braking thrust’ to intentionally slow down.
While the idea of this comet being an alien spacecraft is far-fetched,Dr Loeb says we shouldn’t discount the possibility of a ‘black swan’ event,when something extremely unlikely with a severe impact happens,defying past observations and predictions.
Like,say,3l/ATLAS being a ‘Trojan Horse’ sent to our solar system from another civilisation for nefarious purposes.
Normally,the pressure of sunlight pushes the tail back behind the comet,but if the particles are heavy enough,this may not happen. ‘As you get closer and closer,the solar emission or the flux from the sun increases until eventually that tail starts to get pushed back and joins the rest of the tail.’
Dr Norris said: ‘So the fact that it has an anti-tail is not shocking. [Dr Loeb] has even written a paper that as far as I’m I’m aware,correctly explains why it happens and it has nothing to do in his explanation with aliens.
‘So why he lists it as proof of being aliens? You’d have to ask the guy.’
Dr Norris added that the comet didn’t look like it was ‘braking’ in any case,as it was ‘speeding up because the gravity of the sun is pulling it closer’,and it was in full view rather than doing something where it was harder to observe.
One other ‘slightly unusual thing’ about it is that it has not shown any signs of ‘non-gravitational accelaration’ yet,and is moving exactly as it would be predicted to.
When a comet is pushing out a lot of gas,it tends to give it some thrust which changes its orbit slightly.
Three-panel infrared image of comet 3I/ATLAS taken by Webb on August 6,2025 (Picture:
NASA,ESA,CSA,M. Cordiner)
But if it’s a very heavy comet body,it takes a lot of thrust to push it out of the way,which is probably the reason this hasn’t been detected,Dr Norris said.
‘That’s not particularly shocking,’ he added. ‘It’s interesting,but it’s not like proof of anything. It’s normal.’
The International Asteroid Warning Network has started tracking the path of the comet,something that Dr Loeb said could be evidence that it is seen as a threat.
But Dr Norris was again sceptical,saying it was more likely they were doing so for training and scientific purposes: ‘Nobody would be very happy if we built a system to track hazardous asteroids,and it doesn’t do anything until the one time we need it to.’
He thinks the really exciting thing about these interstellar objects is that one day we may be able to intercept one of them,and physically see what another star system is made from,and how typical ours is.
Given that 3l/ATLAS could be from a star system which formed billions of years before our own,when the galaxy had seen fewer stars living and dying,we would expect its chemical composition to be different to rocks in our own solar system,and it could behave differently as a result.
It’s not visible right now because it’s behind the Sun,and too bright for telescopes to see,but we will get another glimpse from November 2 when the European Space Agency’s JUICE spacecraft trains instruments on it,on its way to studying Jupiter.
According to Nasa,it will reach perihelion,its closest point to the Sun,around October 30,when it will be just inside the orbit of Mars.
It will reappear on the other side of the Sun by early December,when we should be able to see it again from Earth,and will pass reasonably close to Jupiter,but never within the orbit of Earth
Dr Norris said it will be visible until next year,and then will head out of sight towards the far edges of the solar system,then out of it completely within the next decade,and it will ‘continue out in the deep space for potentially millions more years’.
If you have a reasonable amateur telescope.
Towards the end of November,it will be visible again in the early morning around 6am,just before the sun rises.
As time goes on,its separation with the sun will get bigger and bigger,so it will become visible earlier and earlier in the night.
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